‘So for him to get physical and aggressive, unprovoked, is surprising. But I’m sure there’s method to his madness and we’ll find out if the madness has paid off tomorrow night.’

Chisora butted heads with his opponent before the slap, which left a large red mark on the side of Klitschko’s face, and clearly enraged him.Chisora’s trainer Don Charles said he had no idea he was going to do it, and called the slap ‘unacceptable’.When asked if it was pre-meditated, he added: ‘I’m not Dereck Chisora. Like I said, it’s unacceptable.’

Seeing red: Chisora leaves his mark on Vitali Klitschko (Picture: AP)

Beforehand, Klitschko had said he expected an ‘interesting’ fight.’He’s the strongest challenger out there and I always want to prove myself against the best,’ said the German-based Ukrainian.’He is young, wild, aggressive and hungry. He marches forward all the time. The fight will be interesting.’

Chisora, 28, weighed in at 17st 3lbs, just a pound heavier than his lightest weight for a professional bout, and three pounds lighter than his opponent.

He has promised to knock out his 40-year-old opponent in the eighth round.

Klitschko has never been floored in his 43 fights, 40 of which have ended in victory.